The invention concerns the processes for producing plastic laminates using metal laminae.
Plastic laminates usually consist of sheets formed of a number of layers of plastic materials stably associated, generally by pressing, on supports of paper, fabrics, fibreglass or other materials.
The plastic materials used may be of phenol, melamine, epoxy, polyester, silicon, fluoride or others.
To make printed circuits a metal lamina, especially one of copper, is glued onto one or both of their sides during the pressing process.
A pile is formed of packages all Virtually the same, each one comprising a certain number of sheets impregnated with plastic materials and copper laminae placed one on each side of the package.
A metal sheet, of stainless steel or some other type, is placed between each package, and the pile so formed is put in a multiple-plate press which simultaneously provides heat and pressure.
At the end of each heat cycle, in which a temperature of 190.degree. C. may be reached at pressures of up to 100 kg/cm.sup.2 lasting over 100 minutes including a cooling stage to 70.degree.-80.degree. C., a compact and rigid product is obtained the single components of which are closely associated together.
Bearing in mind the many components needed, their nature and dimensions, formation of packages is a somewhat lengthy and complex process; this raises their cost considerably especially in production of laminates for printed circuits. Clearly the presses needed for this process are complex and of low output because of the many heating plates in them, because of the need to produce simultaneously both heat and pressure, with exact timing of these stages, and the need to create, by conduction, uniform temperatures in the various packages making up the pile of which, obviously, only those at each end of it are in contact with the heating plates.
The presence of many plates in the press not only complicates it structure but lengthens the time required for loading and unloading packages while preparation of short runs is made problematic because relatively more costly.